1. Field of the Invention:
The present invention pertains to slide fasteners and methods of assembly thereof, and, more particularly, to slide fasteners configured to prevent splaying of the tapes of the slide fasteners when closed and methods of assembling the sliders on such slide fasteners after top stops are formed on the tapes.
2. Description of the Prior Art:
Slide fasteners conventionally include end stops to limit movement of a slider therefor, the end stops normally including a bottom stop for limiting opening movement of the slider and a top stop for limiting closing movement of the slider. The bottom stop, for many applications, is not externally visible after installation in a garment and is normally installed in a grament where the material is joined such that the bottom stop can have a variety of configurations without irritating the wearer of the garment, without adversely affecting its functional requirements and without hampering installation in a garment. Top stops, however, are normally relatively prominent and visible after installation in garments and are required to be precisely positioned with respect to the fastener elements of the slide fastener to permit separation thereof.
In the past, along with the aesthetic and positioning problems associated with top stops as mentioned above, a particular problem has been encountered at the top portion of the tapes adjacent the top stop in that when the slider is positioned to engage the top stop the diamond post of the slider is disposed between terminal fastener elements such that the upper ends of the slide fastener tapes extending above the top stop are splayed. Splay is further caused by the separation of the top stop members by the diamond post, and this splay is highly undesirable from an aesthetic standpoint as well as causing difficulties in installation of the slide fastener in a garment. These difficulties are accentuated as progress is made in the development of new techniques for quickly and automatically securing slide fasteners to materials, such as electrostatic methods now being incorporated in mass production lines. The problem of splay caused by the diamond post of a slider spacing the terminal fastener elements has been solved by reducing the size of the terminal fastener elements as described in U.S. Pat. No. 3,672,008; however, the problem of splay caused by spacing of the top stop members between the diamond post has not been satisfactorily solved.
Top stops for slide fasteners are conventionally made of bands of metal or other material folded upon themselves and around cords at the inner edges of the slide fastener tapes to which the fastener elements are attached. Such top stops have the disadvantages of being relatively difficult and expensive to apply to the slide fasteners and, additionally, are unattractive as viewed from the exterior side of the slide fastener and are irritating to the wearer of the garment on the interior side of the slide fastener.
With the advent of slide fasteners utilizing fastener elements formed of continuous filaments of deformable plastic material, attempts have been made to provide top stops of similar plastic material to reduce assembly and material costs as well as to permit dyeing of the top stops for aesthetic purposes. Such prior art attempts, however, have not solved the problems involved in the production of top stops for a slide fastener due to the flash and jagged edges resulting from the cutting of single bars of material fused to both tapes simultaneously and the problem of splay caused by spacing of the top stop members. The problem of providing a top stop of plastic material is further made difficult in that the portions of the tapes above the top stops are required to be flexible to permit folding of the tapes during installation in a garment thereby rendering it desirable to have the upper edge of the top stop well defined.
The development of techniques for forming top stops of plastic material on slide fastener tapes has increased the speed of production of slide fasteners; however, speed of production is still relatively slow due to the necessity of forming top and bottom stops during separate operations. The reason for the separate operations is that the bottom stop is desirably secured to the tapes prior to assembly of the slider and the top stop is secured to the tapes after assembly of the slider since the stop members of the top stop are purposely designed so as not to pass through the channels in the slider.
Some of the disadvantages of requiring the slider to be assembled after application of the bottom stop but prior to application of the top stop are that additional equipment and manual handling operations are required, production speed is decreased, slide fasteners cannot feasibly be shipped from the manufacturer until the entire slide fastener is assembled, and broken sliders cannot be replaced without removing the top stop, installing a new slider and applying a new top stop.